Fabricating methods of reflective liquid crystal display and top-emitting oled display

ABSTRACT

Methods for forming a top-emitting organic light emitting display and a reflective type liquid crystal display are provided. The method for forming a top-emitting organic light emitting display comprises: providing a handling substrate; providing a composite layer on the handling substrate; forming an organic light emitting unit on the composite layer; and forming a top electrode on the organic light emitting unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of pending U.S. patent application Ser.No. 12/358,098, filed Jan. 22, 2009 and entitled “Reflective liquidcrystal display, top-emitting OLED display and fabrication methodthereof”, which claims priority of Taiwan Patent Application No.97103678, filed on Jan. 31, 2008, the entirety of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a top-emitting OLED display, and moreparticularly relates to a reflective type display and fabrication methodthereof. The present invention also relates to a reflective typedisplay, and more particularly relates to a reflective type display andfabrication method thereof.

2. Description of the Related Art

There are many advantages of a flexible display such as having strongimpact resistance, a lighter weight and flexibility. In addition,flexible displays have the potential for application in new emergingproducts such as electronic paper, electronic tagging machines, creditcards, roll-up displays, and electronic billboards, in addition toportable electronic devices. Therefore, applications and technologicaladvancements for flexible displays have seen increased research anddevelopment recently. In general, flexible substrate materials areclassified into two categories: plastic substrates of mainly organicmaterials; and metal foil of mainly inorganic materials. Someadvantageous for plastic substrates such as polycarbonate (PC),polyethersulfone (PES), polyarylate (PAR), polyimide (PI), polyethyleneterephathalate (PET) or polyetherimide (PEI), are that they have hightransparency and a relatively high external force distortion tolerance(e.g., may withstand multiple distortions).

However, one disadvantage of plastic substrates is that water vapor ismore easily absorbed by the plastic substrates. Generally, the watervapor barrier rate of plastic substrates is between 101 g/m^(2/)day and100 g/m²/day. On the other hand, the water vapor barrier rate ofTFT-LCDs and OLEDs are respectively 10⁻⁴g/m²/day and under 10⁻⁴g/m²/day.Thus, if the plastic substrates are used, the operating lifespan ofdisplays or products using the plastic substrates will decrease.

As for metal foil substrates, some advantageous are that water vapor isnot easily absorbed by the metal foil substrate and the metal foilsubstrate has flexibility. However, one disadvantage of metal foilsubstrates is that metal foil substrates have a relatively low externalforce distortion tolerance (e.g., unable to withstand multipledistortions).

Therefore, a new method for fabricating a flexible display is called forto alleviate the above constraints.

BRIEF SUMMARY OF THE INVENTION

A detailed description is given in the following embodiments withreference to the accompanying drawings.

An embodiment of the invention discloses a method for forming atop-emitting organic light emitting display, comprising: providing ahandling substrate; providing a composite layer on the handlingsubstrate; forming an organic light emitting unit on the compositelayer; and forming a top electrode on the organic light emitting unit.

Another embodiment of the invention discloses a method for forming areflective type liquid crystal display, comprising: providing a handlingsubstrate; forming a first layer on the handling substrate; forming ametal layer on the first layer; forming a second layer on the metallayer; and forming a thin film transistor array on the second layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1A to FIG. 1E are cross sections of a method for forming atop-emitting organic light emitting display according to an embodimentof the invention, illustrating fabrication steps thereof.

FIG. 2A to FIG. 2B are cross sections of a method for forming areflective type liquid crystal display according to an embodiment of theinvention, illustrating fabrication steps thereof.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

FIGS. 1A to 1E show cross sections of an exemplary embodiment of aprocess for fabricating a top-emitting organic light emitting display200. Wherever possible, the same reference numbers are used in thedrawings and the descriptions to refer to the same or like parts.

Referring to FIG. 1A, a handling substrate 110 is provided and aselective cleaning process is performed for removing pollutants of thehandling substrate 110. The handling substrate 110 can be hard materialssuch as glass, quartz, ceramic or silicon wafer. Then a composite layeris formed on the handling substrate 110, which may include forming afirst layer covering the handling substrate 110, forming a second layercovering the first layer, and forming a metal layer between the firstlayer and the second layer. In an embodiment of the invention, a firstlayer 120 is formed on the handling substrate 110 as a lower substrateof a display. The first layer 120 comprises several polymer materialssuch as polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR),polyimide (PI), polyethylene terephathalate (PET) or polyetherimide(PEI). In one embodiment of the invention, the first layer 120 can beformed by coating processes such as a die coating or table coatingprocess and the like. After coating, the first layer 120 is heated forsolidification on the handling substrate 110.

As FIG. 1B shows, a metal layer 130 can be formed on the first layer 120by an electroless deposition process. In another embodiment of theinvention, the metal layer 130, as a metal foil can be attached to thefirst layer 120 by a hot embossing process, wherein the metal layer 130serves as a lower electrode of the display. Note that the metal layer130 can also be a reflective layer for reflecting any light impingingthereon. The metal layer 130 may include platinum (Pt), palladium (Pd),iridium (Ir), gold (Au), tungsten (W), nickel (Ni), silver (Ag) oraluminum (Al).

Referring to FIG. 1C, a second layer 140 is formed on the metal layer130 as a passivation layer of the metal layer 130. The second layer 140and the first layer 120 can be formed of substantially the samematerials and processes. However, the second layer 140 may be made of apolymer material which differs from a polymer material of the firstlayer 120. Thus, the first layer 120, the metal layer 130 and the secondlayer 140 constitute a composite layer 145. Preferably, the thickness ofthe metal layer 130 is from 0.1 times to 0.5 times the thickness of thefirst layer 120 or the second layer 140. Meanwhile, the thickness of thefirst layer 120 and of the second layer 140 can be the same ordifferent.

Referring to FIG. 1D, an organic light emitting unit 260 is formed onthe composite layer 145. The organic light emitting unit 260 cancomprise a hole injection layer 230, an organic light emitting layer 240and an electron injection layer 250. Following is the manufacturingmethod for the organic light emitting unit 260. Firstly, the electroninjection layer 230 and the organic light emitting layer 240 aresequentially formed on the composite layer 145. The electron injectionlayer 230 and the organic light emitting layer 240 can be formed by aprocess such as a vacuum evaporation process. The material of theelectron injection layer 230 can be such as an m-MTDATA(4,4′,4″-tri{N-3-methylphenyl-N-phenyl-amino)-triphenylamine) and theorganic light emitting layer 240 can be formed by a process such as avacuum evaporation process. The material of the organic light emittinglayer 240 may be a doped organic material. Then, the electron injectionlayer 250 is formed on the organic light emitting layer 240 by a processsuch as a vacuum evaporation process. The material of the electroninjection layer 250 may be formed of metal halide. Following, a topelectrode 270 such as a metal layer can be blanketly formed on theelectron injection layer 250 by processes such as a vacuum evaporationor sputtering process and the metal layer is patterned by processes suchas a photolithography and etching process. The metal layer may includematerials such as aluminum (Al), gold (Au) or platinum (Pt). Finally, atransparent plastic substrate 280 is formed on the top electrode 270 asan upper substrate of the display.

As FIG. 1E shows, the lower surface of the handling substrate 110 whichcomprises the composite layer 145, the organic light emitting unit 260,the top electrode 270 and the transparent plastic substrate 280 isirradiated by a laser beam 60 to separate the first layer 120 from thehandling substrate 110. Since the first layer 120 comprised of polymermaterials is formed on the handling substrate 110, a substantialnon-contact interface may be formed between the first layer 120 and thehandling substrate 110. Therefore, when the lower surface of thehandling substrate 110 is irradiated by the leaser beam 60, an internalstress is produced between the first layer 120 and the handlingsubstrate 110, wherein the first layer 120 peels off from the handlingsubstrate 110. Thus, the composite layer 145, the organic light emittingunit 260, the top electrode 270 and the transparent plastic substrate280 constitute a flexible organic light emitting display 200.

It is noted that since the bottom electrode 130 of the flexible organiclight emitting display 200 is disposed between the first layer 120 andthe second layer 140, the bottom electrode 130 can be protected by boththe first layer 120 and the second layer 140. For example, the secondlayer 140 can prevent possible damage of the bottom electrode 130 duringsubsequent processes. In addition, the bottom electrode 130 is comprisedof metal materials which can prevent water vapor from entering theorganic light emitting unit 260 for increasing the operating lifespan ofthe flexible organic light emitting display 200. Additionally, since theupper and lower substrates (i.e. the first layer 120 and the transparentplastic substrate 280) of the flexible organic light emitting display200 are formed by polymers, possible damage caused by external forces tothe flexible organic light emitting display 200 comprised of a metalfoil substrate and problems normally associated with metal foilsubstrates such as having a relatively low external force distortiontolerance (e.g., unable to withstand multiple distortions) areprevented.

Additionally, the composite layer 145 can be applied to any productwhich can use a flexible substrate with an installed metal layer as afoundation on the flexible substrate. In the aforementioned embodiments,although the descriptions only use the flexible organic light emittingdisplay, the invention is not limited thereto. For instance, thecomposite layer 145 of the embodiment of the invention can be applied toa flexible electronic device such as a Radio Frequency Identification(RFID) and a flexible display device such as an electrophoretic display(EPD) or a field emission display (FED), and are also not limitedthereto.

Referring to FIG. 2, an embodiment of the invention for fabricating areflective type liquid crystal display is shown.

As FIG. 2A shows, a handling substrate 305 is provided and a compositelayer 330 is formed on the handling substrate 305. The materials andmethods for forming the handling substrate 305 and the composite layer330 are the same as the materials and methods for forming the handlingsubstrate 110 and the composite layer 145 in the embodiments of FIG. 1Ato FIG. 1E. Similarly, the composite layer 330 includes a first layer300 covering the handling substrate 305, a second layer 320 covering thefirst layer 300 and a metal layer 310 between the first layer 300 andthe second layer 320. Next, a thin film transistor (TFT) array 210 isformed on the second layer 320. The TFT array 210 can be a bottom gatetype or a top gate type. Although the bottom gate type is used asillustration, the invention is not intended to be limited thereto.

Referring to FIG. 2A again, a plurality of transparent pixel electrodes410 are formed to connect to the TFT array 210. The transparent pixelelectrodes 410 may be an indium tin oxide (ITO) electrode. Following, atransparent plastic substrate 440 is provided as an upper substrate andthe transparent plastic substrate 440 is disposed on opposite sides ofthe handling substrate 305. Next, a common electrode 430 such as an ITOelectrode is formed on the inside transparent plastic substrate 440.Then, a display layer 420 such as a liquid crystal layer is filledbetween the handling substrate 305 and the transparent plastic substrate440. It is noted that the display material of the display layer 420 canbe changed appropriately. For example, the display material such as amicro capsule having electrophoretic characteristics also can be used asthe display material of the display layer 420.

As FIG. 2B shows, the lower surface of the handling substrate 305 whichcomprise the composite layer 330 and the elements of the reflectiveliquid crystal display is irradiated by a laser beam 70 to separate thefirst layer 300 from the handling substrate 305. Consequently, thecomposite layer 330, the TFT array 210, the pixel electrode 410, thedisplay layer 420, the common electrode 430 and the transparent plasticsubstrate 440 constitute a flexible reflective liquid crystal display500.

In this embodiment of the invention, since the metal layer 310 of theflexible reflective liquid crystal display 500 can prevent water vaporfrom entering the display layer 420, the operating lifespan of theflexible reflective liquid crystal display 500 is increased whencompared to a conventional flexible reflective liquid crystal displaywithout the metal layer 310.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

1. A method for forming a top-emitting organic light emitting display, comprising: providing a handling substrate; providing a composite layer on the handling substrate; forming an organic light emitting unit on the composite layer; and forming a top electrode on the organic light emitting unit.
 2. The method as claimed in claim 1, wherein the step of forming the composite layer comprises: forming a first layer on the handling substrate; forming a metal layer on the first layer serving as a bottom electrode; and forming a second layer on the metal layer.
 3. The method as claimed in claim 2, wherein the first layer and the second layer are formed by a coating process.
 4. The method as claimed in claim 1, further comprising a step of removing the handling substrate.
 5. The method as claimed in claim 3, wherein the first layer and the second layer comprise polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), polyimide (PI), polyethylene terephathalate (PET) or polyetherimide (PEI).
 6. The method as claimed in claim 2, wherein the thickness of the metal layer is from 10% to 50% the thickness of the first layer or the second layer.
 7. The method as claimed in claim 2, wherein the metal layer comprises platinum (Pt), palladium (Pd), iridium (Ir), gold (Au), tungsten (W), nickel (Ni), silver (Ag) or aluminum (Al).
 8. The method as claimed in claim 7, wherein the metal layer is formed by a hot embossing or electroless deposition process.
 9. A method for forming a reflective type liquid crystal display, comprising: providing a handling substrate; providing a composite layer on the handling substrate; and forming a thin film transistor array on the composite layer.
 10. The method as claimed in claim 9, wherein the step of forming the composite layer comprises: forming a first layer on the handling substrate; forming a metal layer on the first layer; and forming a second layer on the metal layer
 11. The method as claimed in claim 10, further comprising: forming a plurality of transparent pixel electrodes on the thin film transistor array to connect to the thin film transistor array; providing a transparent plastic substrate opposite to the first layer; forming a common electrode on the transparent plastic substrate and facing the first layer; and forming a liquid crystal layer between the first layer and the transparent plastic substrate.
 12. The method as claimed in claim 10, wherein the first layer serves as a flexible substrate of a display device.
 13. The method as claimed in claim 10, wherein the first layer and the second layer are formed by a coating process.
 14. The method as claimed in claim 9, further comprising a step of removing the handling substrate.
 15. The method as claimed in claim 13, wherein the first layer or the second layer comprise polycarbonate (PC), polyethersulfone (PES), polyarylate (PAR), polyimide (PI), polyethylene terephathalate (PET) or polyetherimide (PEI).
 16. The method as claimed in claim 10, wherein the metal layer comprises platinum (Pt), palladium (Pd), iridium (Ir), gold (Au), tungsten (W), nickel (Ni), silver (Ag) or aluminum (Al)
 17. The method as claimed in claim 16, wherein the metal layer is formed by a hot embossing or electroless deposition process.
 18. The method as claimed in claim 9, wherein the handling substrate comprises glass, quartz, ceramic or silicon wafer. 